Sharks

Imagine a time before dinosaurs, even before the first trees! That's when sharks first started swimming the oceans, over 450 million years ago. These early sharks were much different from the ones we see today. They were smaller, lacked the fancy fins we know, and some even had bony spines!

Over millions of years, sharks kept evolving and changing. Their skeletons, made mostly of cartilage instead of bone, don't fossilize as easily as bones do. But thanks to some lucky finds, scientists know that sharks developed important features like fins for steering and balance, and multiple rows of tough teeth for catching prey.

The Jurassic period, around 200 million years ago, was a real boom time for sharks. This is when most of the modern shark groups, like the great white's ancestors, first appeared. These sharks had even more advanced features, including flexible jaws that could snatch bigger prey and streamlined bodies for faster swimming. Some giants even emerged, like the Megalodon, a monster shark that could grow as long as a school bus!

Sharks have faced many challenges throughout their long history, including mass extinctions that wiped out many other species. But with their strong bodies, keen senses, and constant adaptations, sharks have managed to survive for over 450 million years. Today, they're still top predators in the oceans, and their continued presence reminds us of the amazing power of evolution.